• Transactions of Materials Processing
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• v.11 no.5
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• pp.447-456
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• 2002

A study has been made to investigate the boundary sliding and its accommodation mode with respect to the variation of $\alpha$$_2$/$eta$ volume fraction during superplastic deformation of two-phase Ti$_3$Al-xNb intermetallics. Step strain rate and load relaxation tests have been performed at 950, 970 and 99$0^{\circ}C$ to obtain the flow stress curves and to analyze the deformation characteristics by the theory of inelastic deformation. The results show that the grain matrix deformation and boundary sliding of the three intermetallics containing 21, 50 and 77% in $eta$ volume fractions are well described by the plastic deformation and viscous flow equations. Due to the equal accommodation of both $a^2$ and $\beta$ phases, the accommodation modes for fine-grained materials are in good agreement with the iso-strain rate models. The sliding resistance analyzed for the different boundaries is the lowest in the $\alpha$$_2$/$\alpha$$_2$ boundary, and increases in the order of $\alpha$$_2$/$\alpha$$_2$<< $\alpha$$_2$/$\beta$ = $\beta$/$\beta$, which plays an important role in controlling the superplasticity of the alloys with the various $\alpha$$_2$/$\beta$ phase ratio.

• Journal of the Korean Institute of Navigation
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• v.6 no.2
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• pp.13-33
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• 1982

The NAVSTAR/GPS is a satellite-based navigation system that will provide extremely accurate three-dimensional position and velocity information to users anywhere on or near the earth. This system has been studied primarly for military use and thus the results of studies are seldom obtainable for civilian use up to date. Expecting this system to be opened to civilian use in the future, this paper aims to the collection of basic data of the PN phase modulated communication system adopted in the GPS system by computer simulation. The results of studies are as follows; 1) The PN phase modulation of the speed of 106b/s can be simulated by Fourier summation, the spectrum region which can be restricted is in the region of 0.5-1.5 MHz and spectrum number required is over than 270. 2) By computer simulation, it is verified that optimum r.f filter bandwidth is about 0.3 MHz for the case of $10^6$b/s PN codes phase modulated in 1.575GHz carrier. 3) In case that PN rate to data rate is between 10 and 100, the allowable minimum SNR to demodulate data signal correctly by optimum LPF is about 0.3. It is also verified that the larger the frequency ratio of PN code to the data code, the lower the allowable minimum SNR required.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.1
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• pp.59-69
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• 2000

The characteristics of liquid crystal polymer composite(LCPC) films are possessed of large-area and flexible display, polarizer free, high contrast, wide angle of visual filed and high responsiveness. It is well known that the LCPC films consisting of a continuous LC phase embeded in a three-dimentional network of polymer matrix are formed by photopolymerization-induced phase separation. In this study, we have investigated the point that both liquid crystals and polymer having different properties have to coexiste as composed films. The purpose of this study has been the development of new application with liquid crystals and UV-curable monomers. In the results abtained on the miscibility of nematic liquid crystal and UV-curable resins, difunctional monomer HX-620 turned out to shows the best. From the results abtained on structures, electro-optical properties and dynamic visocoelasticity for LCPC films, the best mixing ratio of monomer to LC mixture were 3/7(photoinitiator; 4wt%) by weight, and this ratio has been provided the most thermal stability for LCPC films. In the results abtained on structure and discoloration properties of LCPC films, it has been demonstrated that consiste of a 8:2 mixture of chiral nematic liquid crystal and HX-620 has the greatest domain and it was the best discoloration.

• Journal of Korea Planning Association
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• v.54 no.1
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• pp.40-51
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• 2019

The ultimate aim of this study is to diagnose the process stage and look at the step change of transition process to see how the step changes. Therefore, in this study, cluster analysis was conducted by examining four types of commercial characteristics such as Retail Homogeneity, Share of Neighbourhood store, Share of chain store, and Share of cafe & Western food store. Through the cluster analysis, three types have been identified. Type1 is the first step which can explain the time before gentrification occurs and when the ratio of neighborhood facilities is the highest. Type2 is the second step that can explain boutique stage where the gentrification occurs. At this time, the ratio of Cafes & Western food restaurant increased and the proportion of neighborhood shops decreased. And Type3, third step is when the mature gentrification occurs. In the analysis of the transition period, it is necessary to monitor the change of the industry in the period from the first stage to the second stage. In the transition period from the second stage to the third stage, It is necessary to constantly monitor such factors as the increase of shops.

• Korean Journal of Community Nutrition
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• v.18 no.6
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• pp.577-587
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• 2013

This study aimed to elicit the variability of appetite and food intake patterns in female college students during different menstrual phases. The craving for certain foods and physiological and psychological symptoms of menstrual phase (pre- and post-menstrual) were investigated by self-administered questionnaire. Three hundred and sixty six students who were 20.9 years old and had $19.8kg/m^2$ of BMI volunteered to participate in this study. Most of the subjects (89.5%) experienced the premenstrual syndrome (PMS) such as irritation, bodily fatigue, nervosity. Symptoms such as tiredness, stomachache, changes in taste and increased appetite were pointed out to be experienced at the onset of the menstrual cycle. The variability of food intake in premenstrual phase, 11.0% of subjects had decreased food intake where as 68.8% had experienced increased intake. The postmenstrual phase, 20.1% had decreased food intake while 45.2% had experienced increased intake due to changes in the appetite. Before starting menstruation, most of the subjects craved for sweets. The group who had experienced abnormal appetite during menstrual phase was significantly high ratio in overweight and obese students (p<0.05). We also observed an association between the PMS score and the variability of eating patterns during the menstrual phase. The students who experienced changing appetite and food intake had significantly high PMS score in the premenstrual phase (p<0.01) and postmenstrual phase (p<0.05). These results suggested a need for future study related to changes in the actual nutrient intake and activity level during the menstrual phase.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1663-1668
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• 2017

A BLDC motor with higher number of phases has several advantages, compared to the conventional three-phase BLDC motors. It can reduce the commutation torque ripple and the iron loss without increasing the voltage per phase and increase the reliability and power density. Higher number of phases increase the torque-per-ampere ratio for the same machine volume and output power by widening the electrical conduction period. In this paper, the proposed seven-phase BLDC motor drive system is made into several functional modular blocks, so that it can be easily extended to other ac motor applications: back-EMF block, hysteresis current control block, pwm inverter block, phase current block, and speed/torque control block. Also in a system of BLDC motor drive, the PI controller has been widely used in the speed controller because of the simple implementation. To obtain a good speed response in a general drive system using the PI controller, the high bandwidth of a controller is established. therefore, in this paper, a Fuzzy controller is applied to the 7-phase BLDC motor drive system in order to improve the speed control performance. The Fuzzy controller is compared with a conventional PI controller through the experiment with respect to speed dynamic responses. These experimental results show that the Fuzzy controller of the 7-phase BLDC motor drive system is superior over the conventional PI controller. The algorithm using the Fuzzy controller can improve a comfortable ride in the field of high performance 7-phase BLDC motor drive applications.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.355-362
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• 2023

A total of 96 weanling pigs with an initial body weight of 5.96 ± 0.08 kg were randomly allocated to two dietary treatments and fed experimental weaning diets for 36 days in three phases; phase 1: day 1 to 7; phase 2: day 8 to 21, and phase 3: day 22 to 36. Treatments consisted of a basal diet (CON) containing 334.0 g/kg dried whey versus a lactic acid (LA) supplemented diet containing 313.6 g/kg dried whey with 10 g/kg LA during phase 1; a CON diet containing 200.0 g/kg dried whey versus an LA diet containing 186.0 g/kg dried whey with 7 g/kg LA during phase 2. During phase 3, both CON and LA groups were fed a diet without dried whey and LA. Pigs fed the LA diet had a higher average daily feed intake ADFI (p = 0.014) and reduced (p = 0.035) gain-feed ratio compared to pigs fed CON diet in phase 2. In phase 3, the average daily gain and feed intake were both increased (p = 0.026 and; p = 0.010, respectively) in the pigs previously fed the LA diet than those fed the CON diet. The apparent total tract digestibility of dry matter and, nitrogen, and the digestible energy were decreased (p < 0.05) in the LA diet group on day 7; however, increased (p < 0.05) digestibility of dry matter and nitrogen and digestible energy was observed at the end of phase 2 and 3. In conclusion, the inclusion of LA was inferred to have improved the average daily gain, feed intake, and nutrient digestibility during the late weanling period of pigs.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.142-147
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• 1997

Purpose: To compare the effectiveness of the in-phase (IP) sequence and the opposed-phase (Op) sequence in the detection of focal hepatic lesions in the single breath-hold hepatic MR imaging with fast gradient T1-weighted pulse sequences. Materials and Methods: IP and OP T1-weighted breath-hold imaging was performed using fast gradient echo sequences in 45 patients referred for known focal hepatic lesions, in which 78 lesions were detected. Three blind readers independently reviewed the images for lesion detectability. The signal-to-noise ratio (SNR) of the liver, the lesion-to-liver contrast-to-noise ratio (CNR) and the liver-to-spleen CNR were also compared. A consensus was reached by three readers to determine which sequence is better in image quality. Results: On OP images, 61(78%), 61(78%), and 63(89%) lesions were correctly identified for reader 1, 2 and 3, respectively. On IP images, 66(85%), 65(83%), and 65(93%) lesions were detected for each reader, respectively. When two image sets were combined, 71(91 %), 69(88 %), and 76(97%) lesions respectively were detected for each reader. In cases of hepatocellular carcinoma, liver-to-Iesion CNR was greater on the OP images(p (0.05), but in other lesions significant difference was not demonstrated. Liver-to-spleen CNR was higher on OP images(p ( 0.1), but the SNR of the liver was higher on the IP images. Conclusion: Use of both IP and OP imaging can be helpful to avoid erroneous missing of some focal hepatic lesions.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.829-834
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• 2011

Lysozyme in egg white functions as bacteriolysis agent and ovalbumin plays a role as antigen in immune system. Egg white analysis methods usually include electrophoresis, gel permeation chromatography and reversed-phase HPLC(RP-HPLC). Among them, RP-HPLC was selected for rapid analysis and C18 column(Agilent, USA) was used as HPLC column. Optimum conditions were searched by changing mobile phase and temperature. Capacity factor and resolution were calculated and compared for various elution conditions. In the isocratic elution, mobile phase volume ratio was changed from 30/70/0.1 to 60/40/0.1(Acetonitrile(ACN)/Distilled water(DW)/Trifluoroacetic acid(TFA)). ACN composition was increased by 10% and temperature was set as $20^{\circ}C$. In the gradient elution, ACN/DW ratio was changed from 10/90 to 60/40 during 20 minute and temperature was varied as 20, 30 and $40^{\circ}C$. In the isocratic elution, three peaks were separated at 50/50/0.1. Lysozyme and ovalbumin were confirmed as first and third peak in three peaks respectively. In the gradient elution, four peaks were separated at $30^{\circ}C$. Lysozyme and ovalbumin were confirmed as first peak and third peak in four peaks respectively.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.18 no.1
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• pp.132-149
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• 1992

This study relates to a microemulsion gel which is applied in various cosmetic preparations because of good appearance, superior stability and a thin, uniform, non-greasy fi Am on the skin. Main object of this study is to elucidate the influence of polyol(clarifying agent and/or coupling agent in microemulsion) on microemulsion and to establish the optimum conditions for microemulsion gel formation in the view of superior consistency, stability, clarity and pick-up from a container. The constituents of the system are composed of water, polar ester oi1, nonionic surfactant and polyol. Using the three-component phase diagram and the tetrahedral-phase diagram, we have investigated the changes of transparence regions, consistency and resonance effect by an impact in microemulsion gel varying in polyol ratio. The results of this study showed that the variation in the content of water and couple ins agent has major influence on the microemulsion gel and the optimum formation region of microemulsion gel is the widest when the ratio of glycerine(coupling agent) to water is 63-75% It is believed that optimum use of polyol seems to be helpful to obtain the microemulsion gel containing maximum amount of oil phase with minimum amount of surfactant which is recently one of the major problems of cosmetic chemists.